The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A157550 Half the number of length n integer sequences with sum zero and sum of squares 648. 1
1, 3, 54, 1830, 68175, 2604105, 72741487, 1575681348, 32584952460, 663445574880, 13119864945495, 250743317040879, 4601891725568592, 80821202263252920, 1358608769903073690, 21985893765384549032, 344851090651019364715 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,2
LINKS
FORMULA
[cache enabling] count(n,s,ss)->count(n,t,tt) where t=s mod n, q=(t-s)/n, tt=ss+2*q*s+n*q^2; count(n,t,tt)=sum[i^2<=tt]{ count(n-1,t-i,tt-i^2) }. a(n)=count(n,0,648)/2.
CROSSREFS
Sequence in context: A323325 A224304 A266523 * A224368 A091826 A091796
KEYWORD
nonn
AUTHOR
R. H. Hardin Mar 02 2009
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 23 22:02 EDT 2024. Contains 372765 sequences. (Running on oeis4.)